Image Credit: AP Photo/Evan Vucci

Mitt Romney will briefly trade the campaign trail for the Holy Land, part of a larger overseas trip that will take the candidate to the Olympics in London for two days before he spends a day and a half in Israel.

Most of the trip will take place on Sunday, July 29 , and he will leave the country on the following day, according to a Romney donor helping to plan the trip. The 29th is the Jewish holiday of Tisha B'av, a day of fasting and mourning in Judaism and the saddest on the Jewish calendar. Unlike another fast day, Yom Kippur or even the Sabbath, observant Jews are allowed to do work and use electricity, but are supposed to keep the destruction of two ancient holy temples as well as the many tragedies the Jewish people have endured in mind.

The source, who agreed to talk with ABC News but did not want to be quoted on the record discussing the trip, said Romney was concerned "no one was offended" by the choice of day, but they felt that according to the Olympics schedule it was the only day to travel to Israel.

"He has enormous concerns about not offending people where religion is concern and it was reflected in Utah when he scheduled Shabbat dinner for us to have who are observant [Jews]," the source who also was at the Park City retreat said. "He spoke to me about having the prayer service [on the Sabbath in Utah]."

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On Sunday night Romney will hold a small fundraiser. Right now only about 30 people are expected, but that number could grow, although it will still most likely be small. The location hasn't been nailed down yet, but it will take a place about an hour after the sun sets, when the fast is over and is open to not only Americans living in Israel, but those visiting.

The website Buzzfeed has a copy of the invitation and the price tag is $50,000 per couple, or if the couple has raised $100,000 they'll also make the cut. The invite requires a U.S. passport to attend the event. Only American citizens can donate to campaigns.

The RSVP on the invitation is Republican fundraiser Lisa Spies, wife of Charlie Spies, founder of pro-Romney superPAC Restore Our Future.

Romney will meet with Prime Minister Benjamin Netanyahu, whom he's known since the 1970s when they worked together at the Boston Consulting Group, and will also mostly likely meet with Israeli opposition leaders.

The source also expects him to visit the Western Wall and Yad Vashem, the country's Holocaust museum and memorial.

"The purpose of the trip is to show the governor's affinity for and caring about the state of Israel and its issues, its concerns. That's the real purpose of him going there," the donor helping to plan the trip told ABC News. "Since he was going to London for the Olympics, he thought it was the right thing to do particularly when you have a president who has not been to Israel for all four years of his presidency and Israel is one of our strong allies, if not our strongest ally, with existential concerns."

The president did visit Israel as a candidate in 2008, just as Romney is doing, but has not made a trip as president.